This invention relates to a phase control device for producing a reference pulse train and a plurality of pulse trains and controlling the latter pulse trains so that each of the latter pulse trains is independently displaced by a desired phase amount from said reference pulse train, with the pulse trains having a predetermined period.
The invention can be preferably embodied in underwater detection systems or phased array radar apparatuses for forming reception or transmission beams.
A prior art phase control system is disclosed in U.S. Pat. No. 3,346,837.
In underwater detection systems, the reception signals caught by for example a linear array of spaced transducers are separately delayed in time with respect to the foregoing ones and combined to form a narrow reception or response beam. As described in U.S. Pat. No. 4,117,487, the reception signals caught can be phase-shifted by mixing the reception signals from the transducers with progressively shifted output signals from a multi-stage, variable phase shifter fed by a local oscillator. The reception signals caught by a plurality of transducers are respectively supplied to one inputs of the mixers and are modulated in the mixers with the progressively shifted pulse signals respectively fed to the other inputs of the mixers. Output signals from the mixers are combined with one another to form a narrow reception beam pointing in a direction. The direction of the reception beam can be changed by varying the phase-shift amount of output signals from the phase shifter. Thus, it is required to provide a device which produces a plurality of pulse trains which are phase-shifted with respect to the preceding ones.